Preparation of chlormaleic anhydride



Patented Dec. 9, 1947 TUNITED STATES PATENT OFFICE PREPARATION orCHLORMALEIC ANHYDRIDE Albert M. Clifford, Stow, Ohio, assignor toWingfoot Corporation, Akron, Ohio, a corporation of Delaware No Drawing.Application June 13, 1945, Serial No. 599,301

This invention relates to the production of monochloro-maleic anhydridefrom maleic anhydride. More specifically, the invention relates. to thedehydrochlorination ofdichloro succinic arr-- hydride prepared by thechlorination of maleic anhydride.

The preparation of monochloro-maleic anhydride by the chlorination andsubsequent dehydrochlorination of maleic anhydride involves the Thefirst reaction generally proceeds at lower temperatures than does thesecond reaction and, accordingly, at higher temperatures thechlorination and dehydrochlorination may take place simultaneously,thereby resulting in the formation of a. mixed product, which isdifiicult to separate into its components. At elevated temperatures thedesired product, monochloro-maleic anhydride, may become furtherchlorinated to form trichloro succinic anhydride which may then losehydrogen chloride to form dichlor-maleic anhydride, Thus it will beapparent that, if monochloro-maleic anhydride is desired, very carefulcontrols are required to prevent the formation of other products and toinsure a high yield of the desired mono-chloro-maleic anhydride. Thepurpose of this invention is to provide a method of preparinmono-chloro-maleic anhydride which results in substantially quantitativeyields.

In application Serial No. 456,087, filed August 25, 1942, by Albert M.Clifiord and John R. Long, there is described and claimed a method ofpreparing substantial yields of the intermediate product,dichloro-succinic anhydride, by chlorination of maleic anhydride attemperatures in excess of 140 C., at which temperature the reaction rateis practicable, but without the dehydrochlorination, which usually takesplace at such temperatures, to form a mixture of monochloro-maleicanhydride and dichloro-succinic anhydride.

Attempts have been made to conduct the chlorination anddehydrochlorination simultaneously in the presence of catalysts attemperatures below those required for the further chlorination of themono-chloro-maleic anhydride. These 2 Claims. (Cl. 260342.6)

methods are described and claimed in application Serial No. 456,090,filed August 25, 1942, by Charles R. Milone. Although the one-stepprocess has many advantages over the two-step process, the latter alsohas its advantages. In either case, however, the selection of propercatalysts for the dehydrochlorination is of major importance. Thus, inapplication Serial No. 456,090

(identified above) and application Serial No.

479,148, filedMarch 13, 1943, by John R. Long and Clyde E. Gleim, thereare described and claimed catalyticmethods for dehydrochlorinatingdichloro-succinic anhydride. The former ap-' plication utilizes alkalineearth metal halides, acyl peroxides, and anhydrides of monocarboxylicacids, while the latter case utilizes secondary or tertiary amines.

The dehydrochlorination of dichloro-succinic anhydride in accordancewith this invention involves homogeneous catalysis in the presence ofany iron salt. The salts of iron which are preferred for reasons ofeconomy are the chlorides and sulfates, either ferric or ferrous saltsbeing used. The use of iron salts as catalysts results in r high yieldsof pure mono-chloro-maleic anhydride, while the use of metallic iron,known to the art, produces tarry masses which contaminate the product,foul the catalyst, and lower the yield of the desired product.

The preferred process uses maleic anhydride as the raw material. Thefirst step is to chlorinate the maleic anhydride by the reaction ofgaseous chlorine at temperatures in excess of C., which promote areasonably rapid rate of reaction, and at a pressure of 10 pounds persquare inch gauge, in accordance with the above-identified applicationSerial No. 456,087. If desired,

the dichloro-succinic anhydride thus prepared may be purified bydistillation at reduced pressures, for example at 2 to 10 mm, totalpressure. The thus purified dichlor-succinic anhydride may then betreated in accordance with this invention by adding a small proportionof an iron salt, for example iron chloride or iron sulfate, preferablyfrom 0.5 to 5.0 percent by weight, and heating the resultin mixture at atemperature in excess of 140 (3., which causes the evolution of gaseoushydrogen chloride and produces substantial yields of mono-chloro-maleicanhydride. If reasonable precautions have been taken to purify theintermediate product, dichloro-succinic anhydride, there will be veryfew impurities in the final product and a substantially quantitativeyield will be obtained.

Example 1 In a glass reactor heated by an oil bath and provided .with astirrer, .a fritted glass chlorine inlet, and a ,packedcolumn outlet,1713 pounds (80 moles) maleic anhydride were melted and mixed with 0.5percent of iron powder. A stream of gaseous chlorine was passed into thevessel for 9 hours at 130-140 C., after which-time the temperature wasraised to the reflux temperature pf 185-190 C. till substantially allHCl had escaped and then the product was distilled .at 110-115 C. atapressure of 40 mm. A yield of 48 percent of mono-chloro-maleic anhydridewas obtained. A considerable quantity of a non-distillable black, tarrysubstance was found associated with the iron residues in the reactionvessel.

Example 2 Utilizing the apparatus of Example '1, 17.3 pounds maleicanhydride was heated .to 140-150" C..with.1.0 percent clean powderediron. Gaseous chlorine was. conducted into the liquid for 23 hours to aweight increase of 8.00 pounds, after which t'he reaction mass washeated slowly to incipient reflux (180-190 'C.) until the main portionof I-ICl had been evolved, and finally distilled at atmosphericpressure, yielding 13.92 pounds, equivalent to 60 percent yieldmono-chloro-maleic anhydride with a boiling .range of 190195 C. Again,there remained a considerable amount of tarry residue.

Example '3 ,In an experiment identical with Example 2, except using 0.26percent powdered iron, the amount of tarry material was so great thatthe reaction product was very viscous and could not be distilled.

Example 4 The experiment of Example 1 was repeated except that 2.5percent of anhydrous iron chloride was used .in place of the powderediron, and chlorination was conducted at 105-110 C. A yield of 22.41pounds or 96 percent of distilled mono-chloro-maleic anhydride wasobtained,

4 B. P. 103-l05 C. 38 mm. with a density of 1.5469 /15.

Example 5 of 7.82 pounds. The reaction product at this point wasgradually heated up to incipient boiling-andfinallydistilled. Thefraction collected "at*190-195 C., amounted to 21.42 pounds,representing a v92 percent 20f theoretical yield.

This :application is a continuation-in-part of application Serial :No.456,086, filed August 25, 1942.

Although the invention has been described with respect to specificimprovements thereof, it is not intended that the details set forthshall be construed as limitations upon the scope of the invention.except to the-extent included in the following claims.

"I claim:

.1. The method of converting..dichlom-sucoinic anhydride tomono-chloro-maleic anhydride which comprises heating thedichloro-succinic anhydride .to a temperature of at least C. inthepresence of ferric chloride.

2'. The method of converting. dichiorosuccinic anhydride tomonochloromaleic .anhydride which comprises heating the dichlorosuccinicanhydride to a temperature of at least 140 C. in the presenceof acatalyst of the group consisting of the chlorides and sulfates of iron.

ALBERT M. CLIFFORD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Dvornikoff Jan. :2-1, 1936 OTHER.REFERENCES Number

